This invention relates to a tire uniformity machine, and more particularly, the invention relates to the hydraulic system for raising and lowering the lower chuck and rim of a tire uniformity machine.
An exemplary tire uniformity machine is depicted in U.S. Pat. No. 4,852,398, the disclosure for which is incorporated herein to form a part of the disclosure for the present invention. The function of the machine is to measure runout and radial and lateral force variations.
The machine includes an upper and a lower chuck which carry rim halves between which tires to be tested are inserted. The lower chuck is connected to a hydraulically-operated piston and cylinder which raises and lowers the lower chuck. A conveyor brings tires to be tested to a centered position between the upper and lower rim halves and conveys tested tires away.
In the testing operation, with the lower chuck down, a tire is brought into position between the two rim halves. The lower chuck is raised, capturing the tire on the lower rim and carrying the tire up to engagement with the upper rim. In some machines, mating nose cones on the upper and lower chucks, respectively, set the vertical spacing between the two chucks. In U.S. Pat. No. 4,852,398 that spacing is set by a combined electronic (LVDT) circuit and hydraulic system. When in position, the tire is inflated. It is engaged by a loadwheel and rotated until the measurement process is completed. Immediately thereafter, the loadwheel is disengaged, the lower chuck is lowered, the tested tire is conveyed away and an untested tire is conveyed into position between the chucks.
Tire makers normally test all passenger vehicle tires before shipping to the automobile manufacturers. All major automobile manufacturers require 100% testing. Thus, there is the need to test an enormous number of tires. Current tire testing machines, such as the machine depicted in U.S. Pat. No. 4,852,398, have an average cycle time of about 23.1 seconds. Such a machine can test on average 155.8 tires per hour. The cost of such a machine is of the order of $300,000. If as little as one second of cycle time can be saved, the capital cost per tire tested of a machine is significantly reduced.